bobandcat wrote:
When I conducted the test at 2600VA (V*A=W),
Definition and calculation
AC power flow has the three components: real power (P), measured in watts (W); apparent power (S), measured in volt-amperes (VA); and reactive power (Q), measured in reactive volt-amperes (VAr).
The power factor is defined as:
In the case of a perfectly sinusoidal waveform, P, Q and S can be expressed as vectors that form a vector triangle such that:
If ? is the phase angle between the current and voltage, then the power factor is equal to
, and:
Since the units are consistent, the power factor is by definition a dimensionless number between 0 and 1. When power factor is equal to 0, the energy flow is entirely reactive, and stored energy in the load returns to the source on each cycle. When the power factor is 1, all the energy supplied by the source is consumed by the load. Power factors are usually stated as "leading" or "lagging" to show the sign of the phase angle.
If a purely resistive load is connected to a power supply, current and voltage will change polarity in step, the power factor will be unity (1), and the electrical energy flows in a single direction across the network in each cycle. Inductive loads such as transformers and motors (any type of wound coil) consume reactive power with current waveform lagging the voltage. Capacitive loads such as capacitor banks or buried cable generate reactive power with current phase leading the voltage. Both types of loads will absorb energy during part of the AC cycle, which is stored in the device's magnetic or electric field, only to return this energy back to the source during the rest of the cycle.
For example, to get 1 kW of real power, if the power factor is unity, 1 kVA of apparent power needs to be transferred (1 kW รท 1 = 1 kVA). At low values of power factor, more apparent power needs to be transferred to get the same real power. To get 1 kW of real power at 0.2 power factor, 5 kVA of apparent power needs to be transferred (1 kW รท 0.2 = 5 kVA). This apparent power must be produced and transmitted to the load in the conventional fashion, and is subject to the usual distributed losses in the production and transmission processes.
professor95 wrote:
Please repost the temperature graphs. I remember them, but do not know where they are.
Here is the temp graph that I posted in early October @ a 2200 watt load.
This picture shows an overview of the enclosure setup.
If you go back to my original post, there is test data at a 2600 watt load that resulted in the engine/generator stumbling after 30 minutes of operation.
The second test was completed at an electrical load of 2200 watts. It was terminated after temps were stable for 4 consecutive readings taken at 5-minute intervals. Total test time was 45 minutes under load and 15 minutes for cool down with the engine off and the enclosure cooling fans running. The stabilized engine air, genhead air and exiting air temperatures were 156, 145 and 152 degrees respectively measured in the same locations as the first test.
Professor Randy's recommendation of not using the generator over 2400 watts near 100 degrees ambient was validated by my tests (2200 watts was OK, 2600 watts was not OK). I have set my limit closer to 2000 watts. That allows me to run my AC continuously with short excursions at higher loads to run the microwave for a couple of minutes.
By the way, generator manufacturer state that power output is reduced 3.5% per 1000 ft. elevation and 2% per 10 degree F temperature rise from a baseline of 85 degrees at sea level. Maximum generator output will not be the same everyday for everyone. It will be dependent on the output reductions noted above.
I sometimes camp near sea level and also as high as 9-10,000 ft elevation. My summer ambient temp can be as high as 110-120 degrees or as low as the 20's in the winter. These extremes, especially altitude, can change the generator output by as much as about 1000 watts.
